1. Field of the Invention
The present invention relates generally to ultra-high frequency diodes working more especially in the 94 GHz band and encapsulated in a case for forming a module which is pre-matched by using the dimensions of the encapsulation case, and relates more particularly to such a pre-matched module for an ultra-high frequency diode with high heat dissipation.
By pre-matched module is meant a module for matching the low impedance of the diode to the high impedance of the surrounding environment, generally air.
2. Description of the Prior Art
It is known that impedance matching is required in ultra-high frequency operation, especially at frequencies close to 100 GHz, for a diode which is to radiate in the space which surrounds it. This matching is particularly advantageous in a radial form for it may be obtained by means of an adequate case.
A pre-matched or pre-tuned module structure is already known for an ultra-high frequency diode, of the Gunn, avalanche or Schottky type. Thus a known prematched module comprises a diode chip fixed inside an encapsulation case formed by a metal base with a central stud or point forming a first connection, a quartz ring surrounding the diode, a metal cap and a second false beam-lead type connection in the form of an non flat metal star the ends of whose arms bear on the face of the quartz ring in contact with the closure cap, and whose center is in contact with the diode chip.
Furthermore, during use of the diode for continuous operation or for pulsed operation, the part of the junction which heats up the most is the part nearest the metal base. There then arises the problem of removing the heat released by the junction when operating. To this end, the diode chip mentioned hereabove is equipped with an integrated heat sink formed by a gold plate of small dimensions, namely 200 microns square and 50 microns thick, which is fixed to the metal base.
However, because of its small dimensions and because of the value of the heat conductivity of gold, of the order of 3.1 W/cm.degree.K. at 200.degree. C., such a gold heat sink does not dissipate as much could be desired the heat generated by the diode during use thereof. Moreover, with this type of heat sink, the total heat resistance of the diode is relatively high, which limits the output power delivered by the diode.